GOODWILL AND OTHER INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Goodwill [Roll Forward]
Goodwill		$ 101,932
Foreign exchange fluctuations		(154)
Decrease due to sale of surface finishes		(695)
Goodwill		101,083	$ 101,932
Sale of Productive Assets [Abstract]
(Gain) on sale of assets		(956)	0	$ 0
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount subject to amortization		85,163	81,336
Accumulated Amortization		51,131	43,816
Indefinite-lived Intangible Assets [Abstract]
Total other intangible assets not subject to amortization		1,170	5,190
Total other intangible assets		86,333	86,526
Other intangible assets [Abstract]
Amortization expense		7,495	7,795	8,176
Estimated future amortization expense [Abstract]
2019		7,119
2020		7,115
2021		7,108
2022		7,108
2023		1,717
Engineered Surface Finishes [Member]
Sale of Productive Assets [Abstract]
Proceeds from Sales of Assets, Investing Activities	$ 3,277
Cash held in escrow	250
(Gain) on sale of assets	$ (956)
In-process Technology [Member]
Indefinite-lived Intangible Assets [Abstract]
Total other intangible assets not subject to amortization		0	4,000
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)				$ 1,000
Other Indefinite-lived Intangibles [Member]
Indefinite-lived Intangible Assets [Abstract]
Total other intangible assets not subject to amortization		1,170	1,190
Product Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount subject to amortization		46,275	42,287
Accumulated Amortization		22,755	17,604
Acquired Patents and Licenses [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount subject to amortization		8,270	8,270
Accumulated Amortization		8,252	8,241
Trade Secrets and Know How [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount subject to amortization		2,550	2,550
Accumulated Amortization		2,550	2,550
Customer relationships, distribution rights and Other [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount subject to amortization		28,068	28,229
Accumulated Amortization		$ 17,574	$ 15,421